Date Added: Sep 2012
A wireless sensor network is capable of sensing physical quantities like pressure, humidity, temperature, real time object and also in the healthcare, and send these reports to the sink (i.e. the central entity), which will process the data and give an output understandable to a human. Wireless sensor network includes hundreds or thousands of sensor nodes. The sensor nodes are having very less energy resources and processing capabilities. Wireless sensor networks are hierarchically clustered, where some of the nodes become cluster heads, and the remaining nodes send their data to cluster head then these cluster head send the data to sink for further processing. The authors assume here that some of the nodes are having more energy than the normal nodes.